The present invention relates to a method and a device for achieving step-by-step feeding by a rotary shaft, comprising one or more well-defined whole turns for the shaft in question. This basic indexing can then be converted by means of direct-acting gear units into parts of a rotation turn for a secondary shaft or shorter or longer rectilinear motions for an optional component. In the latter case, transmitted via a gear rack or equivalent.
The indexing mechanism in question has a number of advantages which make it usable even under harsh conditions. It is thus dynamically balanced, which means that its indexing is independent of external vibrational and gravitational influence, which in turn make it usable in, for example, accessories to modern combat aircraft. It further requires very little space to transmit high torques and, last but not least, it has high repeatability and it is very precise by virtue of the fact that the indexing is effected through mechanical connection and disconnection of, in principle, a single part in a single, precisely defined position.
The working of the indexing mechanism in question incorporates the feature that one or more turns of the rotation of an input shaft is/are relayed as indexing to a second output shaft. By choosing the number of turns which are required to be extracted from the output shaft, a number of different indexings can therefore be obtained. This gives the indexing mechanism in question a very high degree of flexibility.
The step-by-step feeding or indexing is thus achieved according to the invention by mechanical connection between a rotary input motor shaft and a driver, which is in turn connected to a second output shaft which is in line with the motor shaft but totally detached from this, and this second output shaft, following connection, imitating the rotation of the motor shaft for one or more full turns, wholly dependent upon the setting, so as thereafter to be disconnected and braked with immediate effect. According to a preferred embodiment of this system, the motor shaft is directly connected to a cylindrical drive drum arranged concentrically about the same, which drive drum is provided internally with a fluting in the form of grooves or cavities against which a driver which is adjustable between two different positions can be connected and disconnected. In its normal position, the driver, which is thus connected to the second output shaft, is held by an eccentric in engagement with a system-fixed stop lug. As soon as the eccentric is readjusted so that its influence upon the driver ceases, the driver will enter into engagement position against the flutes of the drive drum and will accompany the latter for one or more full turns so as, as soon as the latter re-establishes contact with the eccentric, to be disconnected from the drive drum and with its opposite end enter into engagement with the stop lug, whereupon the latter and the output shaft are simultaneously sharply braked. The sole control unction which is required in this system, over and above the purely mechanical control of the connection and disconnection of the eccentric, is a delay between the activation command and the connection of the driver, which gives the motor time to reach full speed before the driver is coupled together with the drive drum. In those cases in which the drive motor is always switched on, there is obviously no need for any delay whatsoever. It is additionally required that the eccentric shall have been returned to its original position before the driver has completed the intended number of turns.
The driver which is characteristic of the device according to the invention is mounted tiltably about a crankshaft arranged parallel with or vertical to the output shaft and somewhat eccentrically relative to the same, while the driver itself extends at a tangent transversely to this shaft, about which it is tiltable between its two working positions, i.e. alternatively with its end edge facing towards the rotational direction of the motor and in bearing contact against the fluted inner side of the drive drum or with its end edge facing in the rotational direction of the motor and in bearing contact against the fixedly disposed brake lug. In order to tilt over the driver from its position in bearing contact against the fluted inner side of the drive drum, in which position it can be held by, for example, a spring, into its other locked position in which its other end bears against the brake lug, the aforementioned mechanically adjustable eccentric, disposed in a fixed mounting directly beyond the outer edge of the drive drum, can preferably be used, by means of which the driver can be forced over into its other position. For this, the eccentric quite simply lifts the particular end of the driver out of its engagement with the fluting of the drive drum, whereupon the front end of the driver in the rotational direction encounters the stop lug. The fact that the eccentric has a fixedly disposed mounting and the drive drum and the driver, when the latter is connected, rotate about the shafts in question means that the driver and the eccentric have one contact possibility per turn.